1. Field of the Invention
This disclosure relates to the field of containers, particularly to plastic containers which are designed to be stacked and which can formed a “squared” load when palletized.
2. Description of the Related Art
Containers are ubiquitous for the sale of goods in society. The sale of many products is essentially impossible without containers in which to transport the products. While the concept of bulk products (where a user supplies their own container which is filled from a larger container or a processing machine) is popular for some items due to the end consumer's ability to save money on the product by not having to pay for the container it is packed in and the ability of producers to ship products less expensively, most items in today's society are prepackaged in disposable containers prior to sale. In this way, a consumer can simply grab a single container of product for easy transport, purchase, and storage. It also provides the product in a fixed, generally popular, size.
While the container in which items are sold is often of relatively little import to the end consumer (other than for selecting a size), the design of a container can have a large effect on the manufacture, transport, and storage of the product within it. For a manufacturer, performance of the container under certain conditions allows for the product to be provided to the consumer easier or less expensively which can have a dramatic effect on both profitability of the manufacturer and resultant retail price of the product which can improve sales. Improving the container can therefore result in increases to the manufacturers' profitability.
In the first instance, a manufacturer cares about the weight of a container. While heavier containers such as rigid glass containers are generally seen as being stronger and more resilient, heavier containers cost more to construct, as they require more raw ingredients, and, due to the increased weight, also cost more to transport both from the packaging manufacturer to the packaging plant, and (once filled) to the end consumers. This creates increased fuel cost, as well as potentially decreasing the maximum load that can be placed in a truck further increasing logistics costs. Glass containers are also relatively easy to break resulting in increased spoilage.
Today's society is also placing an increased value on conservation. Therefore, containers are in demand which conserve raw materials by using less material in their construction to save on manufacturing costs, that conserve fuel by improving transportation efficiency, that preserve natural resources, and which do not require wasteful consumed products to be used in their transport. Interest in the cost of transportation has significantly increased recently due to recognition that even the most efficient production practices can be foiled by significant transportation losses. Further, it is desired that containers be relatively easily recycled to make new containers. For all these reasons, containers are striving to get lighter and stronger using less material to make containers that still can meet performance necessities for shipping, while allowing for increases in shipping efficiencies.
Because of the various competing desires in packaging, a large number of products are changing from being packaged in glass or metal to being packaged in plastics. Plastics are generally lighter than alternatives, often more resilient, and can be recycled. There are also a wide variety of plastics available which can be selected depending on the products sold in the container. The most common type of plastic containers are probably polyethylene terephthalate (PET) containers which can be blow-molded and can provide for a clear finish which resembles glass.
Plastic containers, are usually significantly thinner than similar glass containers and recent improvements in technology have allowed them to become even thinner while still retaining resilience. The material forming the container neck, however, where a screw top or similar lid joins to the container, is often quite a bit thicker than the material forming the rest of the container. Some of this thickness is to supply strength to the top to resist the torque or other force applied when the lid is screwed on or off, however some of the structure is to be able to support the containers in stacks.
It is well established that it is almost always less expensive to store products in taller vertical space than over more horizontal space. Thus, the ability to stack containers is very important and in most storage scenarios there are always a number of containers of the same size and shape stacked on top of each other. Stacking of containers, however, is often much more complicated than it may seem. Most containers provide for an extended neck which is taller than the main body of the container structure. This neck allows for a lid to easily be screwed, snapped, connected or otherwise positioned on and off. At the same time, however, when containers are stacked, generally a higher container will rest on the lower containers lid or neck due to this vertical extension. When this happens, the weight of that upper container is only distributed across the containers lid (or the rim of the neck if the container is empty) and therefore the shoulder between the neck and the top surface of the container bears significant weight from the stack.
In some cases, the neck is simply unable to bear the necessary weight. In narrow necked containers, the lid or rim may be so small when compared to the base of the upper container that the stack is unstable. Thus, stacking of these types of containers is generally not possible unless there is a cardboard or other sheet placed between the rims of a number of containers in a layer and the bases of the layer above to distribute the force. These type of containers are often, therefore, distributed in packing boxes which only hold a single layer of containers, but can themselves be stacked, or with sheets of cardboard or another segregating material between the layers of the stack to provide for force distribution.
Even in container designs with wider necks, segregating sheets between layers of the stack are often still necessary to prevent the mass of the above containers from being focused too narrowly on the shoulder of the lower container. Thus, when containers have traditionally been stacked for storage or transport, the containers are positioned to form a first layer. This first layer then has a piece of segregation material placed on it (usually a cardboard sheet), and a second layer is placed on the segregation layer. The process is repeated until a desired stack height is obtained. Stacks in these arrangements could result in containers at the second layer being positioned directly over containers in the first layer, or could result in offsets to further distribute force.
While this form of transport is effective, it tends to result in the production of a lot of excess packing material which is discarded by the end user of the containers. The problem exists at two different points. The problem exists first when empty containers are stacked and shipped from the packaging manufacturing plant to the plant where they are to be filled. The problem exists again when the containers a filled and shipped to end retailers. Thus, there is a possibility that the segregation sheets are created and discarded twice for the same load of containers.
Another problem with the transport of empty containers for later filling is that they generally do not have their lids on. Instead, the lids are shipped separately so they do not have to be removed to fill the containers. The lid can serve to better distribute weight across the neck and therefore can provide for some additional strength. Empty containers can, therefore, have greater stacking issues than filled containers, even though the total weight is less. A lid can also provide increased rigidity to the neck simply by having its additional structure on the side of the neck which can add as a structural reinforcement.
Another issue related to the transportation and storage of containers is that they generally need to be palletized in order to be moved efficiently. Most containers are created based solely on the desired resultant size and container look and therefore do not take into account how to be best palletized in order to improve transportation efficiency. Because of this, the containers generally do not occupy a large percentage of the volume in the space above the pallet. This is particularly true of rounded containers but is true even with many squared containers. Basically, the container takes up a greater volume of the space available above the pallet than that which is within its interior volume (its useful space).
This wasted space includes the space around the container's neck, above its top surface, and below the next base (or more particularly the segregation sheet) as well as space between the container and the next on the same level, and the space between the edge of containers and the edge of a pallet. All of this wasted space is effectively shipped instead of extra containers. Thus, the cost to transport each container is increased when containers do not effectively utilize the volume of available space positioned above a shipping pallet.